Assembly of the Photosynthetic Apparatus

Assembly of the photosynthetic apparatus completes the seedling phase of development. The development of this typical plastid structure, which we discussed earlier (page 54), can only take place in light. In darkness, it development goes awry. The phytochrome system is also engaged in the differentiation of the plastids. 

What holds true for the structural elements of the plastids need not be valid for all of the enzyme systems of photosynthesis. A key enzyme in the secondary processes of photosynthesis is carboxydismutase which fixes CO2 into ribulose-1, 5-diphosphate (page 51). The enzyme is already present before the light-dependent differentiation of the plastid structure, at least in rye seedlings. Nonetheless, illumination induces an 

Up to now we have gathered lots of data together and in doing so have come across the participation of phytohormones again and again. Let us 

It all sounds quite plausible. However, in actual fact some of the points are still working hypotheses that need to be proved or refuted. 

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Layered materials are used to produce supramolecular assemblies, in which the properties of the assemblies differ from those of the individual members of the assembly, such that the whole is more than the sum of its components. Such a behavior may be used as a criterion to define a supramolecular system, and nature provides numerous examples. The light-harvesting complex of the photosynthetic apparatus is one such example of outstanding organization. 

Mutants which identify nuclear-encoded functions essential to chloroplast development are valuable resources. Transposon mutagenesis using the Mutator system may provide access to some of the nuclear loci which are essential to chloroplast development and, in so doing, reveal patterns of interaction between the nucleus and organelle in eukaryotic systems. The work presented here lays a foundation for the isolation of nuclear loci essential to the assembly of the major components of the photosynthetic apparatus associated with the chloroplast thylakoid membrane. 

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